Molecular scale electronics, including molecular rectifiers, is an active area of research. A simple electronic device constructed out of a single organic molecule, such as a rectifier, can consist of a donor π-system and an acceptor π-system separated by a sigma-bonded methylene bridge. Semiquantitative calculations can be performed on a hemiquinone to support the concept.
Molecular electrical rectification can also be observed in Langmuir-Blodgett multilayers or monolayers of γ-hexadecylquinolinium tricyanoquino-dimethanide sandwiched between metallic electrodes. However, the mechanism of rectification is not necessarily the donor-insulator-acceptor mechanism. Rather, the envisioned insulator (i.e., sigma-bonded methylene bridge) does not sufficiently isolate the donor pi system from the acceptor pi system.